Right now 4K h.264 is the way things are gonna be done because that's what current hardware supports and that will be followed by VP9 very soon. h.265 is still a long ways off because it needs heavy optimization and tuning for widespread use. VP9 hardware decoding should be hitting GPUs with the Volta GPU from Nvidia, Intel's Skylake, and whatever is coming from AMD around that time.

Support in FFMPEG doesn't mean anything if the performance is bad and right now, it's bad for VP9 and h.265 at all resolutions because there is no offloading to hardware for decode functions and the support in FFMPEG is experimental at best. Every test at low resolution that I've seen says significant CPU usage on high-end machines for both codecs and I can only get VP9 to play back in Chromium/Chrome, despite having the latest builds of VLC and FFMPEG.

"Currently both HDMI and DisplayPort is limited to 30Hz per 4k display so 60Hz monitors like the ASUS PQ321Q have to be a bit creative to get around this limitation. The way that this monitor and others like achieve 60Hz refresh rates is through the use of either DisplayPort in MST (multi stream transport) mode or by using dual HDMI cables to actually run two sub-4k resolution displays side by side on the one monitor. So you are essentially splitting the monitor in half right down the middle with the left side as one display, and the right side as a second display. By doing this, both displays are actually running at 1920x2160 which can operate at 60Hz with current DisplayPort and HDMI specifications."

I'm a few months behind (as always), but I see that ffmpeg supports decoding of h.265 content now.

I'm wondering if anyone has had opportunity to use it and, more specifically, what your experience with 4K has been.

In particular, what CPU/RAM/GPU should we shoot for when building a frontend in Linux for playing 4K?

It's been pretty dead around here lately, but I would appreciate anyone's thoughts on the subject even if you haven't had a chance to play around with it.

Looks like Skylake will be THE big HTPC upgrade for Linux and Windows HTPC enthusiasts. Unconfirmed reports say the Skylake GPU will have both next-gen codecs in the decoder and both next-gen monitor interfaces with the capability to connect 3 4K monitors. Monitor companies will make a big push for 4K displays in 2016 when the new DisplayPort is available along with HDMI 2.0, so save up your dough.